The present invention relates generally to conducting and dissipating heat from a light source, more particularly to effectively dissipating heat from a light source via a heat conducting element and an independent heat dissipating element that allows for economical replacement of an optics module at the end of the lifespan of the light source disposed within the optics module, further particularly to a pendant luminaire, and even more particularly to a pendant luminaire having a light emitting diode (LED) light source and a heat dissipating apparatus.
A variety of different types of light bulbs and other light sources are commercially available. The most common type of light source is the incandescent light bulb, in which electric current is passed through a metal filament disposed in a vacuum, causing the filament to glow and emit light. Another common type of light bulb is the fluorescent light.
A problem with the standard light bulbs having resistive heating elements (e.g. tungsten) is that such a light source expends more energy as heat than as light. Fluorescent lamps run substantially cooler, but have a substantial lag time between when they are initially turned on and when they actually start emitting light, and are often fairly bulky. Halogen lamps are highly efficient, but need to be handled very carefully and generate a considerable amount of heat when manufactured large enough to provide a usable amount of light, even when powered with low voltage (e.g. 12V).
Recent developments in lighting technology involve the expanded use of light emitting diodes (LEDs) that are quite efficient in that they are able to convert virtually all of their supply voltage into light, thereby producing less heat and requiring less overall power consumption. In addition, LEDs may be very small and have an extremely long service life, mainly due to the fact that they operate at cooler temperatures. Compared with a traditional light bulb, an LED lamp may have a lifespan of about 50 to about 100 times that of the traditional light bulb, and the power consumption of such an LED lamp may be about one third to about one fifth that of the traditional light bulb.
General LED light sources are well known in the art. LEDs are light sources based upon a semiconductor structure, specifically a diode structure, which emit incoherent light (which may be in the ultraviolet, visible, or infrared spectrum) when electrical current is passed through the semiconductor junction. One example of such a light source may include phosphors emitting white light. Recent developments in LED technology have increased the output power and efficiency of LED sources so that it is now feasible for them to be utilized in traditional lighting applications previously reserved for incandescent, fluorescent, sodium, and other known lighting technologies.
One current drawback with such LED lamps is that when used to replace a conventional incandescent bulb they must have special driving circuits that convert the incoming alternating-current line voltage to the direct-current low voltage needed by the lamp. Such a circuit is normally a small printed-circuit board that is permanently mounted right in the lamp and to which the LED is normally directly soldered. These circuits typically incorporate a transformer to step down the incoming voltage and a rectifier and similar power-supply elements that produce the necessary steady low voltage. The problem with such a construction is that the driving circuit itself generates heat, particularly when the LED requires some meaningful amperage, albeit at low voltage. Above a temperature of about 25 degrees Celsius, an LED operates less efficiently and produces less light than at lower temperatures. In particular, as the operating temperature progressively increases above 25 degrees Celsius, the light output of the LED progressively decreases. Since the LED itself is typically carried right on the circuit board, when the circuit elements heat up, the LED is heated. Unfortunately the efficiency of an LED falls off rapidly as it gets hot, and thus known LED lamps tend to dim somewhat after they have been in use for a while and their driving circuits have gotten warm.
In order to manage heat, the prior art has attempted to utilize a variety of heat-dissipation techniques, such as an LED attached to a heat sink via heat conductive adhesive, but if the LED stops working, then the entire component must be discarded, making parts replacement costly. Such LEDs are not exchangeable or serviceable and are therefore rendered disposable and very inefficient.
It is desirable that light sources make use of the currently available LED technology due to the significant benefits that such light sources provide including extremely long life, the ability to control output power and spectrum, and a significant reduction in the amount of electrical energy consumed for equivalent light output power. It is also desirable that such light sources be fabricated from materials that are inexpensive and preferably comprise re-usable, recyclable, or replaceable components so as to require a minimum of new raw material and thus preserve limited natural resources. However, utilizing LED light sources in contemporary light sources gives rise to the significant challenge of removing the heat from the LED semiconductor junction and surrounding structures.
While existing LED light sources may be suitable for their intended purpose, there remains, however, a need in the art for an LED light source that provides an improved arrangement for servicing and/or replacement of the illuminating element independent from the heat dissipating element so as to be environmentally friendly and lower overall maintenance and/or replacement costs relative to present illumination apparatus, while at the same time providing for ease of manufacturing.
This background information is provided to reveal information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention.